Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$96.70	5.354%	$101.8773	$101.88	$101.90	$101.90
Purchase #2	$81.28	10.245%	$89.6071	$89.61	$89.60	$89.60
Purchase #3	$69.26	11.307%	$77.0912	$77.09	$77.10	$77.10
Purchase #4	$59.78	6.291%	$63.5408	$63.54	$63.55	$63.50
Purchase #5	$220.43	3.372%	$227.8629	$227.86	$227.85	$227.90
Purchase #6	$219.40	5.667%	$231.8334	$231.83	$231.85	$231.80
Purchase #7	$152.78	11.685%	$170.6323	$170.63	$170.65	$170.60
7 purchase totals =	$899.63		$962.4450	$962.44	$962.50	$962.40